Arthroscopes and similar optical instruments, such as endoscopes, are used in medical applications, such as surgery and examination, as well as in non-medical applications that similarly involve visual inspection of a confined or inaccessible space that constitutes the working area. Although the present invention is described here with reference to an arthroscope or similar instrument employed for surgery, the invention may be useful for other applications and is intended to embrace all suitable variations.
Over the last fifteen or more years, minimally invasive surgery has become a mainstream surgical technique. Within the orthopedic field, in particular, arthroscopy and similar techniques that employ devices such as arthroscopes have become the most common surgical procedures. Minimally invasive surgery is less painful for the patient and, in most instances, can be performed more quickly and safely than surgery that requires greater invasion of the patient's body; other benefits of minimally invasive surgery include that administration of anesthesia is simpler for minimally invasive surgery, that patients heal more quickly, that hospital stays may be reduced in length or even eliminated, and that the procedures are more cost effective.
The value of using minimally invasive surgical techniques may be limited by the capabilities of the arthroscopes, endoscopes and other principal optical instruments employed. In particular, the rather limited field of view afforded by even the best available instruments that satisfy the dimensional and other requirement of surgical applications has limited the useful scope of minimally invasive surgical techniques. Typically, the larger the field of view, the greater the usefulness of the instrument for most applications.
Several methods for widening the field of view offered by arthroscopic/endoscopic instruments have been proposed, and some have been more successful than others, in view of challenges such as precision of construction, precision of relative movements, space requirements, optical distortions, and elimination of undesired ambient light. Various proposals involve different movable arrangements of optical elements provided in the input end of the instrument. Such an arthroscope incorporates a control mechanism that allows the operator to vary the view of the arthroscope by adjusting external controls that manipulate the movable arrangement of optical elements accordingly. Designing the control mechanism is challenging because the components that manipulate the movable arrangement of optical elements must provide sufficiently precise control and fit in the arthroscope.
An additional challenge in designing the control mechanism is to minimize, and preferably eliminate, the risk of leaks in the housing to seal moisture out of the system. Typically, reusable medical devices are sterilized by autoclaving. Autoclaving involves steam sterilization that normally reached 135 degrees Celsius. It is very difficult to seal steam out of the housing. If an endoscope control system is sealed with O rings or other sealing devices, in most cases, eventually enough moisture will leak into the housing to create condensation on the internal lenses during the cooling period following autoclaving. There is no convenient way to remove the condensation, so once the lenses are occluded, typically the arthroscope is no longer functional. Thus, it is desirable to seal the lenses in a leakproof housing. A housing through which moving parts, such as the components of common control mechanisms, penetrate cannot generally be guaranteed to be completely sealed so that it is leakproof, especially as parts like seals and gaskets wear down over time.
There is a need for a variable view arthroscope with a sealed housing. In particular, there is a need for a control mechanism for a variable view arthroscope that permits the housing to be completely sealed. In this specification and in the appended claims the term “arthroscope” means and should be interpreted to include an endoscope or any other similar optical instrument, whether used for surgery or other applications.